# NASA ASJ — Axisymmetric Subsonic Jet

Validation case from the **NASA TMR Collaborative Testing Challenge 2022** ([turb-prs2022](https://tmbwg.github.io/turbmodels/turb-prs2022.html)). Acoustic reference Mach M_jet ≈ 0.5.

## Required metrics
1. **u/U_jet vs. x/D_jet** — centerline velocity decay
2. **u/U_jet vs. y/D_jet at 5 specified stations** — radial velocity profiles
3. **u'v'/U_jet² vs. y/D_jet at 5 specified stations** — Reynolds-stress profiles

Compared with the Bridges & Wernet ARN (Acoustic Reference Nozzle) consensus PIV dataset.

## Folder layout
```
NASA_ASJ/
├── baseline_komegasst/   k-ω SST integral profiles (.dat + .csv)
├── highfidelity/         ARN PIV experiment + NASA WIND SSTV CFD reference
└── plots/                Pre-rendered comparison figures + plot_profiles.py
```

The full transient OpenFOAM case (mesh, time-averaged fields, post-processing) is hosted separately on the heavy CFD-asset Hugging Face dataset linked in the paper.

## Solver / setup
- **Solver**: `rhoPimpleFoam` (compressible transient, with `fieldAverage` to produce mean fields)
- **Turbulence model**: `kOmegaSST` (baseline, no augmentation)
- **Time-averaging window**: last half of run, captured in `*Mean` fields
- **Mach**: M_jet = 0.5
- **Why transient**: the jet shear layer is convectively unstable; a steady SIMPLE iteration does not converge cleanly. Time-stepping with field averaging is the equivalent of a converged steady RANS solution here.

## Submission format
Three files matching the columns of the bundled baseline:
- `ASJ_u_vs_x.csv`         — `zone`, `x/Dj`, `u/Uj` (single zone, centerline)
- `ASJ_u_at5stations.csv`  — `zone`, `u/Uj`, `y/Dj` (one zone per station: `x/Djet=2`, `5`, `10`, `15`, `20`)
- `ASJ_uv_at5stations.csv` — `zone`, `u'v'/Uj^2`, `y/Dj` (same zone structure)

Then `python plots/plot_profiles.py` overlays the baseline + reference + your model.